Continuous plasma carrier coating process and apparatus for preparing same

ABSTRACT

The disclosure relates to processes of preparing coated carrier particles by means of plasma activation and apparatus for use thereof.

BACKGROUND

The disclosure relates to processes of preparing coated carriers using plasma. Currently, the coated carrier particles are prepared using powder coating processes, as disclosed in, for example, U.S. Pat. No. 8,309,293, the disclosure of which is hereby incorporated by reference in its entirety. The typical powder coating processes require multiple steps including the step of mixing (tumble blend) the carrier core and the polymer, and the step of coating the carrier core with the polymer at an elevated temperature.

There is a need to simplify the current coating process. The process of the present disclosure has benefits over the powder coating process by eliminating the step of mixing the carrier core and the polymer, thereby reducing the process time and labor cost. The process is also more environmentally friendly.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of a plasma carrier coating process according to certain embodiments of the disclosure.

SUMMARY OF THE INVENTION

According to embodiments illustrated herein, there is provided a process for preparing a coated carrier particle for use in developer compositions, comprising providing a carrier core in a carrier gas; producing a plasma; irradiating the carrier core with the plasma to generate a charged carrier core; and continuously coating the charged carrier core with a polymer to form a polymeric coating.

In embodiments, there is provided a process for preparing a coated carrier particle for use in developer compositions, comprising providing a metal core in a carrier gas; producing a plasma by microwave energy; irradiating the carrier core with the plasma to generate a charged carrier core; and continuously coating the charged carrier core with a polymer to form a polymeric coating.

The present disclosure also provides an apparatus for preparing a coated carrier particle of claim 1, comprising a reaction tube for feeding of a carrier core and a carrier gas; a wave guide for producing plasma; a microwave resonant cavity for exposing the carrier core and carrier gas to the plasma; a precursor zone for coating the charged carrier core; and a tubular furnace for adhering the polymeric coating to the charged carrier core.

DETAILED DESCRIPTION

The disclosure relates to processes of preparing coated carrier particles by means of plasma activation and apparatus for use thereof. The coated carrier particles can be used in developer compositions, such as xerographic developer composition. The disclosure provides a process for continuously coating a polymer on a carrier core by means of plasma activation.

Embodiments of the disclosure will be explained in more detail below by means of the drawings. The examples illustrated herein are provided to facilitate understanding of the disclosure but not to limit the scope of protection as defined in the claims. FIG. 1 shows a waveguide based plasma system for preparing coated carrier particles. Carrier core 1 and gas 2 are fed into a reaction tube 3 that passes through a microwave resonant cavity 4. The microwave plasma 5 is generated in a wave guide 6 and sent into the microwave resonant cavity 4 where it is exposed to the carrier core 1 and gas 2 that has passed into the microwave resonant cavity from the reaction tube 3. At the intersection between the reaction tube 3 and the microwave resonant cavity 4, the plasma of gas is ignited. The microwave plasma (or plasma) 5 activates the surface of the carrier core 1. The activated carrier core 1 then passes through the polymer precursor zone 7 where it is exposed to a powder cloud of a coating polymer 8. The polymer 8 is attracted to carrier core surface due to electrical charge. The polymer 8 forms a thin coating 8 a on the carrier core 1 as it passes through. The carrier core with polymer on the surface then passes through a tubular furnace which rapidly melts the polymer coating and adhere it to the surface and producing coated carrier 9. The temperature at the tubular furnace is typically in the range of from about 175° C. to about 290° C.

The process of the present disclosure does not require the mixing of the carrier core and the coating polymer.

The term “continuously” refers to the fact that there are no major disruptions or gaps in depositing the polymer onto the activated (or charged) carrier core. The thinkness and coverage of the polymeric coating continuously processed as the carrier core passes through the polymer precursor zone.

The term “plasma” as used herein is defined to include any portion of the gas or vapors which contain electrons, ions, free radicals, dissociated and/or excited atoms or molecules produced.

When sufficient energy is added to a gas, the gas becomes ionized and enters a plasma state. The excitation energy supplied to a gas to form a plasma (i.e., ionized gas) can originate from electrical discharges, direct currents, radio frequencies, microwaves, or other forms of electromagnetic radiation. In certain embodiments, the plasma can be generated using microwave energy in a waveguide, for example, in a cylindrical or rectangular waveguide. The microwave plasma can be generated using a microwave with a frequency of from about 1 Mega Giga Hertz to about 300 Giga Hertz, from about 10 Mega Hertz to about 200 Giga Hertz, or from about 2.5 Mega Hertz to about 90 Giga Hertz. Typically, the microwave plasma can be generated at atmospheric pressure. The gerenation of microwave plasma may not require any heating. The temperature of the microwave resonant cavity can be in the range of from about 150° C. to about 260° C.

Microwave plasma is a type of plasma that has high frequency electromagnetic radiation in the GHz range, and is capable of exciting electrodeless gas discharges. If applied in surface-wave-sustained mode, they are especially well suited to generate large-area plasmas of high plasma density. If they are both in surface-wave and resonator mode, they can exhibit a high degree of spatial localisation. This allows to spatially separate the location of plasma generations from the location of surface processing.

Generally, microwave plasma discharges if the electric field at a given frequency exceeds the intrinsic breakdown field strength of the gas.

A plasma can be fully ionized or partically ionized. Typically, a plasma is in the range of between about 1% and about 10% ionized when it comes in contact with the carrier core. The degree of ionization of a plasma is the proportion of atoms that have lost or gained electrons, and is controlled mostly by the temperature. Even a partially ionized gas in which as little as 1% of the particles are ionized can have the characteristics of a plasma.

When a plasma comes in contact with a carrier core (i.e., irradiation with a plasma), its energy acts on the surfaces of the carrier core and changes certain properties, such as surface energy. Upon irradiation with a plasma, the surface energy of the surface of the carrier increases. Surface energy quantifies the disruption of intermolecular bonds that occur when a surface is created. In the physics of solids, surfaces must be intrinsically less energetically favorable than the bulk of a material (i.e., the molecules on the surface have more energy compared with the molecules in the bulk of the material).

Upon irradiation with a plasma, the carrier core carries electric charges and ions (charged carrier core), thereby attracting the surrounding polymer powder onto its surface, and forming a polymeric coating. A plasma is sometimes referred to as being “hot” if it is nearly fully ionized, or “cold” if only a small fraction (e.g., less than 5%, or from about 0.01% to about 2%) of the gas molecules are ionized. The temperature of the plasma can be adjusted by adusting the wavelength of the microwave. The wavelength of the microwave is typically ranged from about 0.3 GHz to about 300 GHz, from about 3 GHz to about 30 GHz.

Gas

A variety of gases may be fed into the plasma generator to form a plasma, which include nitrogen, oxygen, argon, hydrogen. In general, nitrogen or argon may be used if an inert atmosphere is desired; oxgen may be used if an oxidizing atmosphere is desired; and hydrogent may be used if a reduction atmosphere is desired. In certain embodiments, gas mixtures containing two or more gases may not be used for producing the plasma.

Carrier Core

Various suitable solid core materials may be used for the carriers of the present disclosure. Characteristic core properties include those that, in embodiments, will enable the toner particles to acquire a positive charge or a negative charge, and carrier cores that will permit desirable flow properties in the developer reservoir present in an electrophotographic imaging apparatus. Other desirable properties of the core include, for example, suitable magnetic characteristics that permit magnetic brush formation in magnetic brush development processes; desirable mechanical aging characteristics and desirable surface morphology to permit high electrical conductivity of any developer including the carrier and a suitable toner.

The carrier core may include a metal, a polymer, or mixtures thereof.

Examples of metal carrier cores that may be used include iron and/or steel, such as, atomized iron or steel powders available from Hoeganaes Corporation or Pomaton S.p.A (Italy), and ID Hoganas Corporation (Sweden); a ferrite including an alloy of ferric iron oxide and a metal, such as, copper, zinc, nickel, manganese, magnesium, calcium, lithium, strontium, zirconium, titanium, tantalum, bismuth, sodium, potassium, rubidium, cesium, strontium, barium, yttrium, lanthanum, hafnium, vanadium, niobium, aluminum, gallium, silicon, germamium, antimony, combinations thereof and the like, specific example of ferrites include, such as, Cu/Zn-ferrite containing, for example, about 11% copper oxide, about 19% zinc oxide and about 70% iron oxide, including those commercially available from D.M. Steward Corporation or Powdertech Corporation, and those commercially available from IEDOWA (Japan), Ni/Zn-ferrite available from Powdertech Corporation, Sr (strontium)-ferrite, containing, for example, about 14% strontium oxide and about 86% iron oxide, commercially available from Powdertech Corporation, and Ba-ferrite; magnetites, including those commercially available from, for example, Hoganas Corporation (Sweden), and IEDOWA (Japan); nickel; combinations thereof, and the like. Other suitable carrier cores are illustrated in, for example, U.S. Pat. Nos. 4,937,166, 4,935,326, and 7,014,971, the disclosure of each of which hereby is incorporated by reference in entirety, and may include granular zircon, granular silicon, glass, silicon dioxide, combinations thereof and the like. Examples of polymer carrier cores that may be used include U.S. Pat. No. 4,565,765: U.S. Pat. No. 5,582,951: U.S. Pat. No. 6,355,194, the disclosure of each of which hereby is incorporated by reference in entirety.

In embodiments, suitable carrier cores may have an average particle size of, for example, from about 20 μm to about 400 μm in diameter, from about 30 μm to about 300 μm in diameter, in embodiments, from about 40 μm to about 200 μm in diameter.

Polymeric Coating

The polymeric coating on the carrier core includes a polymer. Generally, any thermoplastic polymer or thermoset plastic polymer can be used as materials of the polymeric coating. Examples of polymers include, but are not limited to, acrylates, polyvinylidine flouride, nylons (i.e., polyamides), urethanes, and mixtures thereof, and the like.

In embodiments, a polymer utilized as the coating of a carrier core may be derived from a monomer including an aliphatic cycloacrylate and an acidic acrylate monomer, and optionally carbon black. Suitable aliphatic cycloacrylates which may be utilized in forming the polymer coating include, for example, cyclohexylmethacrylate, cyclopropyl acrylate, cyclobutyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, cyclopropyl methacrylate, cyclobutyl methacrylate, cyclopentyl methacrylate, combinations thereof, and the like. Suitable acidic acrylate monomers which may be utilized in forming the polymer coating include, for example, acrylic acid, methacrylic acid, beta-carboxyethyl acrylate, combinations thereof, and the like.

The aliphatic cycloacrylate may be present in a copolymer utilized as a polymeric coating of a carrier core in an amount of from about 85% by weight of the copolymer to about 99% by weight of the copolymer, in embodiments from about 90% by weight of the copolymer to about 97% by weight of the copolymer. The acidic acrylate may be present in such a copolymer in an amount of from about 0.1% by weight of the copolymer to about 5% by weight of the copolymer, in embodiments from about 1% by weight of the copolymer to about 3% by weight of the copolymer.

The polymeric coating can be applied to the carrier core as particles of a size from about 40 nm to about 200 nm in diameter. The polymeric coating thickness can be controlled to from about 50 mils to about 350 mils, from about 100 mils to about 250 mils, or from about 145 mils to about 195 mils. Coating thickness and coating coverage can be controlled by weight of polymer(s) used, heating time and temperature.

In embodiments, the coated carrier particle may contain from about 0.5% to about 10% by weight, in embodiments, from about 0.7% to about 5% by weight, from about 1% to about 4% of the polymeric coating of the present disclosure.

Colorants

In embodiments, the polymeric coating on the carrier core may include one or more colorants, such as dyes, pigments, mixtures of dyes, mixtures of pigments, mixtures of dyes and pigments, and the like. The colorant may be included in the polymeric coating in an amount of, for example, about 0.1 to about 5% by weight of the carrier core, from about 0.3 to about 3 wt % of the toner, from about 0.5 to about 2% by weight of the carrier core, although amounts outside those ranges may be utilized.

As examples of suitable colorants, mention may be made of carbon black like REGAL 330®; magnetites, such as Mobay magnetites MO8029™, M08060™; Columbian magnetites; MAPICO BLACKS™ and surface treated magnetites; Pfizer magnetites CB4799™, CB5300™, CB5600™, MCX6369™; Bayer magnetites, BAYFERROX 8600™, 8610™; Northern Pigments magnetites, NP-604™, NP-608™; Magnox magnetites TMB-100™, or TMB-104™; and the like. As colored pigments, there may be selected cyan, magenta, yellow, red, green, brown, blue or mixtures thereof. Generally, cyan, magenta, or yellow pigments or dyes, or mixtures thereof, are used. The pigment or pigments are generally used as water based pigment dispersions.

Specific examples of pigments include SUNSPERSE 6000, FLEXIVERSE and AQUATONE water based pigment dispersions from SUN Chemicals, HELIOGEN BLUE L6900™, D6840™, D7080™, D7020™, PYLAM OIL BLUE™, PYLAM OIL YELLOW™, PIGMENT BLUE 1™ available from Paul Uhlich & Company, Inc., PIGMENT VIOLET 1™, PIGMENT RED 48™, LEMON CHROME YELLOW DCC 1026™, E. D. TOLUIDINE RED™ and BON RED C™ available from Dominion Color Corporation, Ltd., Toronto, Ontario, NOVAPERM YELLOW FGL™, HOSTAPERM PINK E™ from Hoechst, and CINQUASIA MAGENTA™ available from E.I. DuPont de Nemours & Company, and the like. Generally, colorants that may be selected are black, cyan, magenta, or yellow, and mixtures thereof. Examples of magentas are 2,9-dimethyl-substituted quinacridone and anthraquinone dye identified in the Color Index as CI-60710, CI Dispersed Red 15, diazo dye identified in the Color Index as CI-26050, CI Solvent Red 19, and the like. Illustrative examples of cyans include copper tetra(octadecyl sulfonamido) phthalocyanine, x-copper phthalocyanine pigment listed in the Color Index as CI-74160, CI Pigment Blue, Pigment Blue 15:3, and Anthrathrene Blue, identified in the Color Index as CI-69810, Special Blue X-2137, and the like. Illustrative examples of yellows are diarylide yellow 3,3-dichlorobenzidene acetoacetanilides, a monoazo pigment identified in the Color Index as CI 12700, CI Solvent Yellow 16, a nitrophenyl amine sulfonamide identified in the Color Index as Foron Yellow SE/GLN, CI Dispersed Yellow 33 2,5-dimethoxy-4-sulfonanilide phenylazo-4′-chloro-2,5-dimethoxy acetoacetanilide, and Permanent Yellow FGL. Colored magnetites, such as mixtures of MAPICO BLACK™, and cyan components may also be selected as colorants. Other known colorants may be selected, such as Levanyl Black A-SF (Miles, Bayer) and Sunsperse Carbon Black LHD 9303 (Sun Chemicals), and colored dyes such as Neopen Blue (BASF), Sudan Blue OS (BASF), PV Fast Blue B2G01 (American Hoechst), Sunsperse Blue BHD 6000 (Sun Chemicals), Irgalite Blue BCA (Ciba-Geigy), Paliogen Blue 6470 (BASF), Sudan III (Matheson, Coleman, Bell), Sudan II (Matheson, Coleman, Bell), Sudan IV (Matheson, Coleman, Bell), Sudan Orange G (Aldrich), Sudan Orange 220 (BASF), Paliogen Orange 3040 (BASF), Ortho Orange OR2673 (Paul Uhlich), Paliogen Yellow 152, 1560 (BASF), Lithol Fast Yellow 0991K (BASF), Paliotol Yellow 1840 (BASF), Neopen Yellow (BASF), Novoperm Yellow FG 1 (Hoechst), Permanent Yellow YE 0305 (Paul Uhlich), Lumogen Yellow D0790 (BASF), Sunsperse Yellow YHD 6001 (Sun Chemicals), Suco-Gelb L1250 (BASF), Suco-Yellow D1355 (BASF), Hostaperm Pink E (American Hoechst), Fanal Pink D4830 (BASF), Cinquasia Magenta (DuPont), Lithol Scarlet D3700 (BASF), Toluidine Red (Aldrich), Scarlet for Thermoplast NSD PS PA (Ugine Kuhlmann of Canada), E. D. Toluidine Red (Aldrich), Lithol Rubine Toner (Paul Uhlich), Lithol Scarlet 4440 (BASF), Bon Red C (Dominion Color Company), Royal Brilliant Red RD-8192 (Paul Uhlich), Oracet Pink RF (Ciba-Geigy), Paliogen Red 3871K (BASF), Paliogen Red 3340 (BASF), Lithol Fast Scarlet L4300 (BASF), combinations of the foregoing, and the like.

Additives

In embodiments, the polymeric coating on the carrier core may further include an additive. Examples of these additives include metal oxides such as titanium oxide, silicon oxide, aluminum oxides, cerium oxides, tin oxide, mixtures thereof, and the like; colloidal and amorphous silicas, such as AEROSIL®, metal salts and metal salts of fatty acids inclusive of zinc stearate, calcium stearate, or long chain alcohols such as UNILIN 700, and mixtures thereof.

It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also, various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, and are also intended to be encompassed by the following claims.

While the description above refers to particular embodiments, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of embodiments herein.

The presently disclosed embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of embodiments being indicated by the appended claims rather than the foregoing description. All changes that come within the meaning of and range of equivalency of the claims are intended to be embraced therein.

EXAMPLES Example 1

Ferrite carrier precursor, 100 gram per min of Ferrite core EMC1010, is carried by carrier gas such as nitrogen. Nitrogen gas microwave plasma which ignited at the interaction between intersection tube and cavity activate the surface of Ferrite core in the reaction tube and the core expose to polymer precursor, mixture of SLS/Carbon black/Melamine at a ratio of about 80.4%/9.6%/10% by weight, fed to the reaction tube at a rate of 1.22 gram per min to have 1.22% of coating weight on the surface of the Ferrite core. Polymer coated carrier then expose to instantaneous heat to melt the polymer on the Ferrite core to produce powder coated carrier.

The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others. Unless specifically recited in a claim, steps or components of claims should not be implied or imported from the specification or any other claims as to any particular order, number, position, size, shape, angle, color, or material.

All the patents and applications referred to herein are hereby specifically, and totally incorporated herein by reference in their entirety in the instant specification. 

What is claimed is:
 1. A process for preparing a coated carrier particle for use in developer compositions, comprising: providing a carrier core in a carrier gas; producing a plasma; irradiating the carrier core with the plasma to generate a charged carrier core; and continuously coating the charged carrier core with a polymer to form a polymeric coating.
 2. The process of claim 1, wherein the plasma is produced by microwave energy.
 3. The process of claim 1, wherein the carrier core has an average particle size of from about 20 μm to about 400 μm in diameter.
 4. The process of claim 1, wherein the carrier core comprises a metal, a polymer, or mixtures thereof.
 5. The process of claim 4, wherein the metal is selected from the group consisting of iron, steel, ferrites, magnetites, nickel, and mixtures thereof.
 6. The process of claim 1, wherein the polymer is selected from the group consisting of acrylates, polyvinylidine flouride, nylons, urethanes, and mixtures thereof.
 7. The process of claim 1, wherein the the polymeric coating comprises a copolymer derived from monomers comprising an aliphatic cycloacrylate and an acidic acrylate monomer.
 8. The process of claim 7, wherein the aliphatic cycloacrylate is selected from the group consisting of cyclohexylmethacrylate, cyclopropyl acrylate, cyclobutyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, cyclopropyl methacrylate, cyclobutyl methacrylate, cyclopentyl methacrylate, and mixtures thereof,
 9. The process of claim 7, wherein the acidic acrylate monomer is selected from the group consisting of acrylic acid, methacrylic acid, beta-carboxyethyl acrylate, and mixtures thereof.
 10. The process of claim 7, wherein the aliphatic cycloacrylate is present in an amount of from about 85% by weight to about 99% by weight of the copolymer.
 11. The process of claim 7, wherein the acidic acrylate monomer is present in an amount of from about 0.1% by weight to about 5% by weight of the copolymer.
 12. The process of claim 1, wherein the the polymeric coating is present in an amount of from about 0.5% to about 10% by weight based on the total weight of the coated carrier particle.
 13. The process of claim 1, wherein the polymeric coating has a thickness of from about 50 mils to about 350 mils.
 14. The process of claim 1, wherein the process does not require a mixing of the carrier core and the coating polymer.
 15. A process for preparing a coated carrier particle for use in developer compositions, comprising: providing a metal core in a carrier gas; producing a plasma by microwave energy; irradiating the carrier core with the plasma to generate a charged carrier core; and continuously coating the charged carrier core with a polymer to form a polymeric coating.
 16. The process of claim 15, wherein the metal core comprises ferrites.
 17. The process of claim 15, wherein the polymer is selected from the group consisting of acrylates, polyvinylidine flouride, nylons, urethanes, and mixtures thereof.
 18. The process of claim 15, wherein the the polymeric coating is present in an amount of from about 0.5% to about 10% by weight based on the total weight of the coated carrier particle.
 19. The process of claim 15, wherein the polymeric coating has a thickness of from about 50 mils to about 350 mils.
 20. An apparatus for preparing a coated carrier particle of claim 1, comprising a reaction tube for feeding of a carrier core and a carrier gas; a wave guide for producing plasma; a microwave resonant cavity for exposing the carrier core and carrier gas to the plasma; a precursor zone for coating the charged carrier core; and a tubular furnace for adhering the polymeric coating to the charged carrier core. 